1. Field of the Invention
This invention relates to a method for detecting amino acids for application to sequence determination from the amino (N) terminal of a protein. More particularly, it relates to a method for detecting amino acids with high sensitivity by using an amino compound containing a radioactive iodine isotope, for example, iodohistamine or a fluorescent amino compound, for example, aminopyrene or aminofluorene.
2. Description of the Prior Art
For the detection of amino acids in the final step of the phenylisothiocyanate method according to Edmon, P., Acta. Chem. Scand. 10 761 (1956), which is an N-terminal sequence determination method, it has been a usual practice as shown in FIG. 2 that thiazolinone derivatives are treated with an acid to form phenylthiohydantoin (PTH) derivatives and these derivatives are determined spectrophotometrically.
Although the prior art method for spectrophotometrically detecting PTH derivatives is simple and convenient as detection means, it cannot fully cope with a recent trend toward more highly sensitive analysis of a protein with a smaller amount of specimen.
For the high sensitivity detection of amino acids, methods of using .sup.32 S PITC labelling or .sup.135 I PITC labelling are shown in the following publication, PITC standing for phenylisothiocyanate:
W. G. Lauer, Fundamental Techniques in Virology, Eds. K. Habel and N. P. Salgman p. 379 (1969) Academic Press N.Y.
C. J. Burrell, P. D. Cooper, J. M. Swann, Aust J. Chem. 28 2289, (1975).
In above methods, radioactive isotope derivatives take part in the main reaction in the Edman degradation method. If high radioactivity is used for the purpose of realizing high sensitivity, not only radioactive disintegration increases, which adversely affects a yield itself in the Edman amino acid sequence determination, but also the contamination of the environment occurs.